The Surface Characteristics and Micro-Shear Bond Strength of Resin Cement to Digitally Produced Permanent Indirect...

Recent advancements in digital dentistry have facilitated the widespread use of both CAD/CAM milling and 3D printing technologies for the fabrication of indirect restorations. Despite their increasing clinical application, comparative data regarding their surface characteristics and bonding performance with resin cements remain limited.

This study aims to investigate the surface properties and micro-shear bond strength (µSBS) to resin cement of digitally produced permanent indirect resin composites.

Three different CAD/CAM milling materials, vita enamic (VE), cerasmart (CE), lava ultimate (LU), and 3D-printed materials saremco-els (ELS), varseo smile crown plus (VSC), and formlabs permanent crown (FLP) were used. Seventy-two test samples (n = 12; 6 groups) were prepared with dimensions 15 × 4 × 1.5 mm. The surface roughness of the test materials was evaluated by a contact profilometer. Surface properties, topographies, and elemental composition were examined by scanning electron microscopy (SEM), atomic force microscopy (AFM), and EDS. After dual-cure resin cement was condensed into the samples, a µSBS test was performed, and fracture modes were determined under a stereomicroscope. The Mann-Whitney U test and the Kruskal-Wallis test were utilized for statistical analysis. P < 0.05 was considered statistically significant.

The surface roughness values for the 3D-printed composite resin materials were generally higher than those of the CAD/CAM groups. When the measurements were examined, the surface roughness values of the 3D-printed groups ranged from 0.37 ± 0.05 μm to 0.51 ± 0.27 μm, while the CAD/CAM milling groups' values were from 0.36 ± 0.36 μm to 0.29 ± 0.08 μm. The highest µSBS value was observed in the FLP group (32.15 ± 14.29 MPa), whereas the lowest was found in the VE group (18.06 ± 5.47 MPa). There was no statistically significant difference in the µSBS results except for the FLP-VE and CE-VE groups (P < 0.05). Cohesive and mixed failures were only found in the 3D-printed groups.

The 3D-printed permanent composite resins exhibited higher surface roughness. However, they demonstrated comparable micro-shear bond strength and favorable failure types, suggesting their clinical potential as alternatives to CAD/CAM milling composites.